JP2001267181A - Chip type solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise a volumetric efficiency and to reduce in size and to improve operability by surely connecting a lead wire for an anode to an anode terminal. SOLUTION: An anode terminal 9 and a cathode terminal 10 are formed over front and rear surfaces and a side face of an insulating board 8 of conductive films. A wire 27 is connected to the terminal 9 via a conductive adhesive 28. The board 8 is arranged on a lower surface of a capacitor element 3. The wire 27 is connected to a lead wire 2 for the anode of the element 3 by resistance welding. The terminal 10 is connected to a silver layer 26 of the element 3 via a conductive adhesive 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type solid electrolytic capacitor.

[0002]

2. Description of the Related Art A tantalum solid electrolytic capacitor using a porous tantalum sintered body as an anode metal is generally widely used as a chip type solid electrolytic capacitor incorporated in a video camera, a cellular phone, and the like. I have.

FIG. 5 shows a conventional example of this type of chip type tantalum solid electrolytic capacitor. The tantalum solid electrolytic capacitor 1 includes a capacitor element 3 made of a tantalum sintered body provided with an anode lead wire 2 and an outer terminal (also referred to as a resin outer terminal) 6 in which a part of the anode terminal 4 and the cathode terminal 5 is made of an insulating resin. Coated with The tantalum sintered body is formed by pressing a fine powder of tantalum in which one end of an anode lead wire 2 of tantalum or the like is embedded in advance by a pressing mold to form a pressed body (raw pellet). The raw pellets are manufactured by heat sintering in vacuum. Thereafter, a dielectric coating layer is formed on the entire surface of the tantalum sintered body, and a solid electrolyte layer and a cathode layer are sequentially formed thereon to manufacture the capacitor element 3. Next, the anode terminal 4 is connected to the anode lead wire 2 by resistance welding or the like, and the cathode terminal 5 is connected to the outermost cathode layer of the capacitor element 3 by the conductive adhesive 7.
Thereafter, a part of the anode terminal 4 including the connection part A between the capacitor element 3 and the anode lead wire 2 and a part including the connection part B of the cathode terminal 5 with the cathode layer are covered with the exterior 6. Thus, the tantalum solid electrolytic capacitor 1 is manufactured. In addition, the anode terminal 4 and the cathode terminal 5 are pulled out to the outside from the opposing side surfaces of the exterior 6 and are bent downward, and further, the front ends thereof are bent toward the lower surface side of the exterior 6 to form a land portion of the printed wiring board. Connected by soldering.

[0004]

The above-mentioned conventional tantalum solid electrolytic capacitor 1 is covered with a sheath 6 to protect a connection point A between the anode lead wire 2 and the anode terminal 4, and the anode terminal 4 is covered with the sheath 6. It is pulled out to the side of. For this reason, the length L of the connection point A becomes longer, and the capacitor 1
If there are restrictions on the external dimensions of the
The size of the capacitor element 3 must be reduced by that much in order to secure it inside. Therefore, the ratio of the volume of the capacitor element 3 occupied in the exterior 6 (hereinafter referred to as volume efficiency) is low, and there is a problem that it is difficult to increase the capacitance as compared with the external dimensions.

[0005] In order to solve such a problem, the present applicant has previously proposed a solid electrolytic capacitor according to Japanese Patent Application No. 11-210190. In the solid electrolytic capacitor 12, as shown in FIG. 6, an anode terminal 9 and a cathode terminal 10 extending from the front surface to the rear surface through the side surface are formed at both ends in the longitudinal direction of the insulating substrate 8 by a conductive film. An insulating substrate 8 is provided on the lower surface of the capacitor element 3. The anode terminal 9 is connected to the anode lead wire 2, and the cathode terminal 10 is connected to the cathode layer of the capacitor element 3.

In such a structure, it is not necessary to adopt a structure in which the anode terminal 9 is drawn out to the side of the exterior, so that the length of the connection portion between the anode lead wire 2 and the anode terminal 9 can be shortened. As a result, if the outer dimensions of the capacitor 12 are the same, the capacity can be increased by enlarging the shape of the capacitor element 3, and the outer dimension of the capacitor 12 can be reduced if the shape of the capacitor element 3 is fixed. And there is an advantage that the size can be reduced. Further, since the insulating substrate 8 is formed of an insulating material and has a function as an exterior similarly to the resin exterior 6, the thickness of the resin exterior 6 can be reduced by the thickness of the insulating substrate 8. Therefore, the volume efficiency of the capacitor 12 can be improved without increasing the thickness of the entire capacitor due to the insulating substrate 8.

However, in the solid electrolytic capacitor 12 shown in FIG. 6, the anode lead wire 2 and the anode terminal 9 are connected.
Are connected by the conductive adhesive 13 or the fuse, thus causing the following problems. When the conductive adhesive 13 is used, a step of removing the oxide film of the anode lead wire 2 is required, so that not only the number of steps increases but also the conductive adhesive 13 is applied only to the removed portion. It is extremely difficult, requires skill and is inferior in workability. Further, in order to fill the gap between the anode lead wire 2 and the anode terminal 9 with the conductive adhesive 13, not only the amount of the conductive adhesive 13 used increases but also the cost increases, but also the capacitor element 3 is insulated. Expansion and shrinkage of the resin or the like that occurs when the resin is covered with the exterior 6 made of a resin may cause a connection failure between the anode lead wire 2 and the anode terminal 9 and the conductive adhesive 13, and may cause peeling. Inferior.

On the other hand, when a fuse is used instead of the conductive adhesive 13, it is necessary to connect by wire bonding or resistance welding. There was a problem of lack of sex. In other words, in the case of wire bonding, a fuse cannot be directly connected to the anode lead wire 2 made of tantalum, and it is necessary to apply gold plating or the like to the lead wire in advance. Become. When connecting by resistance welding,
Since the fuse itself is thin and small, high accuracy is required due to dimensional variations and inclinations of the capacitor element 3 and workability is poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to achieve high volumetric efficiency and downsizing while ensuring that the anode lead wire and the anode terminal are securely connected. An object of the present invention is to provide a chip-type solid electrolytic capacitor that can be connected.

[0010]

According to a first aspect of the present invention, there is provided a porous sintered body made of a valve metal having a lead wire for an anode, a dielectric coating layer, a solid electrolyte, Layer and a cathode layer are sequentially formed as a capacitor element,
In a chip-type solid electrolytic capacitor in which an anode terminal and a cathode terminal are connected to the anode lead wire and the cathode layer, respectively, and a part of these terminals and the capacitor element are covered with a sheath made of an insulating resin, the anode terminal and the cathode are connected. An insulating substrate having terminals formed from the front surface to the side surface to the rear surface is provided on the lower surface of the capacitor element, a wire is provided on the upper surface side of the anode terminal, and the wire and the anode lead wire are connected by resistance welding. The cathode terminal and the cathode layer are connected by a conductive adhesive.

A second invention provides a capacitor element by sequentially forming a dielectric coating layer, a solid electrolyte layer and a cathode layer on the surface of a porous sintered body made of a valve metal having an anode lead wire, In a chip-type solid electrolytic capacitor in which an anode terminal and a cathode terminal are connected to the anode lead wire and the cathode layer, respectively, and a part of these terminals and the capacitor element are covered with a sheath made of an insulating resin, the anode terminal and the cathode are connected. An insulating substrate having terminals formed from the front surface to the rear surface through the side surface is provided on the lower surface of the capacitor element, a wire is connected to the anode lead wire by resistance welding, and the wire and the anode terminal are connected by wire bonding. And the cathode terminal and the cathode layer are connected by a conductive adhesive.

In the present invention, since the wire and the anode lead wire are connected by resistance welding, there is no need to remove an oxide film, apply gold plating, or apply a conductive adhesive as a pre-process. Excellent workability and large joint strength. In addition, the influence of variations and inclinations of the capacitor elements and expansion and contraction of the insulating resin caused during molding is small, and a reliable connection can be obtained. Since the anode terminal is formed over the front and back and side surfaces of the insulating substrate, it is not drawn out to the side surface of the exterior. Further, since the wire is embedded in the exterior, it is not drawn out to the side surface of the exterior. Therefore, the connecting portion between the anode lead wire and the wire does not become long. Wire bonding provides high connection reliability. Since the insulating substrate has a function as an exterior similarly to the resin exterior, the thickness of the resin exterior is reduced by the thickness of the insulating substrate. As the wire, for example, 42
Alloys (alloys of iron and nickel), copper and the like are used.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a sectional view showing a first embodiment of a chip-type solid electrolytic capacitor according to the present invention. The same components as those described in the section of the related art are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

In these figures, in this embodiment, an example is shown in which a porous sintered body made of a valve metal is applied to a chip type tantalum solid electrolytic capacitor (hereinafter also referred to as a capacitor) 20 formed of tantalum. Show. The capacitor 20 includes a porous tantalum sintered body 21 made of a valve metal in which one end of an anode lead wire 2 made of a tantalum wire is embedded, and a dielectric coating layer 22 is formed on the entire surface thereof. Further, a solid electrolyte layer 23 made of manganese dioxide or an organic conductive polymer such as polypyrrole and polyaniline and a cathode layer 24 are sequentially formed thereon to form the capacitor element 3.

The tantalum sintered body 21 is formed by pressing a fine powder made of tantalum together with the anode lead wire 2 by a pressing mold to form a pressed compact (raw pellet).
The raw pellets are produced by sintering in a vacuum. The cathode layer 24 is formed by a carbon layer 25 and a silver layer 26.

On the lower surface of the outer casing 6, a thickness of 0.1 mm is provided.
An insulating substrate 8 of about 1 to 0.3 mm is provided. The insulating substrate 8 is made of a heat-resistant material, particularly a thermosetting resin such as a phenol resin, an epoxy resin, or an unsaturated polyester resin, or an insulating material such as a ceramic. A terminal 10 is formed.

The anode terminal 9 is formed by plating of copper or the like or by applying and drying a conductive paste. The anode terminal 9 is formed continuously from the front surface of the insulating substrate 8 through the side surface to the back surface. Wire 2 to lead 2
7 electrically and mechanically. Wire 2
7 is a metal which can be directly bonded to tantalum, for example, 4
2 made of an alloy (alloy of iron / nickel), copper, etc., and the upper surface of the tantalum sintered body 21 of the anode lead wire 2
Connected by resistance welding to the lower surface of the part protruding from
The lower surface is connected to a portion of the anode terminal 9 which covers the surface side of the insulating substrate 8 by a conductive adhesive 28. Here, an example is shown in which the wire 27 is formed in a chip shape having a square cross section, but the present invention is not limited to this, and a wire having a circular cross section may be used.

The cathode terminal 10 is formed by plating of copper or the like or by applying and drying a conductive paste, similarly to the anode terminal 9, and is formed continuously from the front surface to the rear surface of the insulating substrate 8 via the side surfaces. The surface side is the silver layer 2
6 are connected by a conductive adhesive 7.

Tantalum sintered body 2 of lead wire 2 for anode
A washer 29 is attached to a base end portion of the portion protruding from 1. This washer 29 is used for the solid electrolyte layer 23.
In the forming step, when the tantalum sintered body 21 is immersed in the manganese nitrate solution, it is used to prevent the manganese nitrate solution from adhering to the portion of the anode lead wire 2 protruding from the tantalum sintered body 21. A disk-shaped material made of a highly water-repellent and highly insulating material such as ethylene tetrafluoride, silicone rubber, and silicone resin is used.

The exterior 6 for sealing the capacitor element 3 with resin covers only the surface of the insulating substrate 8, and the wire 27 is embedded therein. Therefore, the wire 27 is not exposed on the side surface of the exterior 6.

In such a capacitor 20, the portions formed on the lower surface side of the insulating substrate 8 of the anode terminal 9 and the cathode terminal 10 at the time of mounting are connected to the lands of the printed wiring board by soldering.

In order to manufacture the tantalum solid electrolytic capacitor 20 having the above-described structure, first, one end of the anode lead wire 2 is inserted into a pressing mold and filled with fine tantalum powder. Is compressed and integrated with the anode lead wire 2 to produce a raw pellet. Next, the raw pellets are heated at a predetermined temperature (14
By baking at a temperature of about 00 to 1500 ° C. for a certain time (about 20 to 30 minutes), a porous tantalum sintered body 21 integrally provided with the anode lead wire 2 is produced. Next, a washer 29 is attached to the anode lead wire 2, and a dielectric coating layer 22 is formed on the surface of the tantalum sintered body 21 by anodic oxidation. In this anodic oxidation, the tantalum sintered body 21 is immersed in an electrolytic solution composed of an acid solution such as nitric acid, phosphoric acid, acetic acid, oxalic acid, and the like.
This is performed by applying a voltage of about one hundred to several tens of volts.

Next, the tantalum sintered body 21 on which the dielectric coating layer 22 is formed is impregnated with a manganese nitrate solution and adhered thereto, and then heated at 200 to 350 ° C. to form a carbon dioxide on the dielectric coating layer 22. Manganese (solid electrolyte layer) is deposited. Such manganese nitrate liquid impregnation, adhesion and thermal decomposition operations are repeated more than ten times to form a manganese dioxide layer which is a solid electrolyte layer. After forming the manganese dioxide layer, it is re-chemically formed using a liquid such as acetic acid to form a solid electrolyte layer 23 having a predetermined thickness.

Next, a carbon paste is applied and dried to form a carbon layer 25. Further, a conductive silver paste is applied thereon and dried to form a silver layer 26, whereby the capacitor element 3 is manufactured.

Next, the anode lead wire 2 and the wire 27 are connected by resistance welding. The resistance welding does not require a pretreatment step of removing an oxide film on the anode lead wire 2 and the wire 27.

Next, the insulating substrate 8 on which the anode terminal 4 and the cathode terminal 10 are formed is mounted on the lower surface of the capacitor element 3.
The production of the insulating substrate 8 is performed in parallel with the production of the capacitor element 3. The anode terminal 9 and the cathode terminal 10 are simultaneously formed by plating (or applying and drying a conductive paste). Such a capacitor element 3 of the insulating substrate 8
After the conductive adhesives 7 and 28 are applied to the surface side of the anode terminal 9 and the cathode terminal 10, the capacitor element 3 is placed on the insulating substrate 8 and the anode terminal 9 and the wire 27 are conductively bonded. The cathode terminal 10 and the silver layer 26
Are connected by a conductive adhesive 7.

Next, the insulating substrate 8 was attached to the lower surface, the anode terminal 9 was connected to the anode lead wire 2 via the wire 27, and the cathode terminal 10 was connected to the silver layer 26 by the conductive adhesive 7. By molding the capacitor element 3 with a thermosetting synthetic resin by a transfer molding method, a chip-shaped tantalum solid electrolytic capacitor 20 covered with the exterior 6 is manufactured.

As described above, in the present invention, the wire 27 is interposed between the anode lead wire 2 and the anode terminal 9 and the wire 27 and the anode lead wire 2 are connected by resistance welding, so that the oxidation occurs during welding. There is no need to remove the coating or apply gold plating, and the connection work is easier and workability is better than when connection is made using a conductive adhesive or a fuse. In addition, in the case of resistance welding, compared to the case of connection using a conductive adhesive or a fuse, there is less influence due to accuracy, variation, inclination, expansion, contraction, and the like that occur during molding with an insulating resin, and high bonding is achieved. Since the strength is obtained, the connection can be reliably performed, and the reliability of the connection can be improved.

Further, the wire 27 is embedded in the exterior 6,
Since it is not drawn out to the side surface of the exterior 6, the connecting portion between the anode lead wire 2 and the wire 27 can have the length of the protruding portion of the anode lead wire 2 projecting from the tantalum sintered body 21. Therefore, the length of the capacitor 20 can be shortened, and the size can be reduced. Further, if the external dimensions of the capacitor 20 are not changed and the same size as the conventional one is used, the shape of the capacitor element 3 can be increased, so that the capacity can be increased. Further, since the insulating substrate 8 is formed of an insulating material and also has a function as an exterior similarly to the resin exterior 6, the thickness of the resin exterior 6 can be reduced by the thickness of the insulating substrate 8. Therefore, the volume efficiency of the capacitor 20 can be improved without the entire thickness of the capacitor 20 being increased by the insulating substrate 8.

FIG. 2 is a sectional view showing a second embodiment of the present invention. In this embodiment, a through hole 33 is formed in the insulating substrate 8, and the anode terminal 9 is formed by plating or a conductive film on the inner peripheral surface of the through hole 33 and the peripheral portion of the through hole 33 on the back surface of the insulating substrate 8. Further, a flanged wire 34 formed of a 42 alloy, copper or the like into a pin shape is press-fitted into the through hole 33 from the lower surface side of the insulating substrate 8 and electrically connected to the anode terminal 9. The lower surface of the lead wire 2 is connected by resistance welding. In this case, the electrical connection between the anode terminal 9 and the wire 34 was made only by press-fitting, but soldering may be used together if necessary. The other structure is exactly the same as that of the first embodiment, and the description thereof is omitted.

Also in such a structure, since the anode lead wire 2 and the wire 34 are connected by resistance welding, the same effects as those of the first embodiment can be obtained. Further, since the wire 34 is connected to the anode terminal 9 by press-fitting into the through hole 33, the connection operation between the anode terminal 9 and the wire 34 is easy.

FIG. 3 is a sectional view showing a third embodiment of the present invention. In this embodiment, the lead wire 2 for the anode protrudes from the tantalum sintered body 2 and
A wire 36 made of an alloy, Ni, or the like is connected by resistance welding, and the wire 36 and the anode terminal 9 formed on the insulating substrate 8 are connected by a thin wire 37 made of gold, aluminum, or the like. The fine wires 37 are connected by wire bonding. The other structure is exactly the same as that of the first embodiment described above, and the description thereof is omitted.

Also in such a structure, since the anode lead wire 2 and the wire 36 are connected by resistance welding, the same effects as those of the first embodiment can be obtained. In addition, since wire bonding is a technology established in IC manufacturing technology, high connection reliability can be obtained.

[0034]

Next, an embodiment according to the present invention and a conventional example will be described. Table 1 below shows the product dimensions of the capacitor according to the first embodiment (Example) and the conventional capacitor (conventional example) shown in FIG.

[0035]

[Table 1]

FIGS. 4A and 4B show mounting areas of the capacitor according to the first embodiment and the conventional capacitor shown in FIG. Table 2 shows dimensions and mounting areas of the capacitors of the embodiment and the conventional example.

[0037]

[Table 2]

As is clear from Tables 1 and 2, according to the capacitor of the present invention, the external dimensions and mounting area of the capacitor can be reduced as compared with the conventional capacitor shown in FIG. I have.

The capacitors according to the second and third embodiments were fabricated and compared with the conventional capacitor shown in FIG. 5 in terms of external dimensions and mounting area. , And the same results as in Table 2 were obtained.

In each of the above-described embodiments, an example is shown in which a porous sintered body is formed of tantalum. However, the present invention is not limited to this, and the present invention is not limited to this. A sintered body formed of a valve metal may be used.

[0041]

As described above, in the chip type solid electrolytic capacitor according to the present invention, the insulating substrate having the anode terminal and the cathode terminal formed from the front surface to the side surface to the back surface is disposed on the lower surface of the capacitor element. Since a wire was provided on the upper surface side of the anode terminal and this wire and the lead wire for the anode were connected by resistance welding, a pre-treatment step of removing an oxide film or applying gold plating was not required, and a conductive adhesive was used. The connection work is easier and the workability is excellent as compared with the case where connection is made by using a fuse or a fuse. In addition, in the case of resistance welding, there is little influence of variation and inclination of the capacitor element, expansion and shrinkage of the exterior caused at the time of molding, and the connection can be securely performed, and the conventional connection using a conductive adhesive or a fuse can be performed. Higher reliability is obtained compared to capacitors. Also, since the wire is interposed between the anode lead wire and the anode terminal, there is no need to pull out the wire or the anode terminal to the side of the exterior, and the length of the connection point between the anode lead wire and the wire is reduced. Can be shortened. Therefore, the length of the capacitor can be reduced, and the size can be reduced.
If the external dimensions of the capacitor are not changed, the size of the capacitor element can be increased. Therefore, in this case, the capacity is increased, and the volume efficiency of the capacitor can be improved. Furthermore, since the insulating substrate is formed of an insulating material and also has a function as an exterior as well as the resin exterior, by reducing the thickness of the resin exterior by the thickness of the insulation substrate, the thickness of the entire capacitor is reduced by the insulation substrate. No thickening.

[0042] Also, in the invention in which a wire is connected to the anode lead wire by resistance welding and the wire and the anode terminal are connected by wire bonding, the same effect as the above-described invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a chip-type solid electrolytic capacitor according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

FIGS. 4A and 4B are diagrams showing mounting areas of an example product and a conventional example product.

FIG. 5 is a cross-sectional view of a conventional chip-type tantalum solid electrolytic capacitor.

FIG. 6 is a cross-sectional view of another conventional chip-type tantalum solid electrolytic capacitor.

[Explanation of symbols]

2 ... Anode lead wire, 3 ... Capacitor element, 4 ... Anode terminal, 5 ... Cathode terminal, 6 ... Outer package, 7 ... Conductive adhesive, 8 ...
Insulating substrate, 9 anode terminal, 10 cathode terminal, 21 tantalum sintered body, 22 dielectric coating layer, 23 solid electrolyte layer, 24 cathode layer, 25 carbon layer, 26 silver layer, 2
7: wire, 28: conductive adhesive, 33: through hole, 34: wire, 36: wire, 37: fine wire.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Suzuki 16th Ohira Okuma, Miharu-cho, Tamura-gun, Fukushima Prefecture Inside the Miharu Plant, Hitachi AIC Co., Ltd. 16 Ohira, Hitachi AIC Co., Ltd. Miharu Plant (72) Inventor Takeshi Yoshihiro 16th Omi, Ohara, Miharu-cho, Tamura-gun, Fukushima Prefecture Hitachi-AC Co., Ltd. Miharu Plant F-term (reference) 5E082 AA01 AB09 BC32 BC39 EE02 EE13 EE23 EE32 EE45 FF05 FG03 FG16 FG27 FG44 GG10 HH27 HH47 JJ06 JJ15 JJ25 LL29

Claims (2)

[Claims] 1. A capacitor element by sequentially forming a dielectric coating layer, a solid electrolyte layer and a cathode layer on the surface of a porous sintered body made of a valve metal and having a lead wire for an anode, and forming a capacitor element. In a chip-type solid electrolytic capacitor in which an anode terminal and a cathode terminal are connected to a wire and a cathode layer, respectively, and a part of these terminals and the capacitor element are covered with an exterior made of an insulating resin, An insulating substrate formed over the back surface through the side surface is disposed on the lower surface of the capacitor element, a wire is provided on the upper surface side of the anode terminal, and the wire and the anode lead wire are connected by resistance welding, A chip-type solid electrolytic capacitor, wherein a terminal and the cathode layer are connected by a conductive adhesive. 2. A capacitor element by sequentially forming a dielectric coating layer, a solid electrolyte layer and a cathode layer on a surface of a porous sintered body made of a valve metal having an anode lead wire to form a capacitor element. In a chip-type solid electrolytic capacitor in which an anode terminal and a cathode terminal are connected to a wire and a cathode layer, respectively, and a part of these terminals and the capacitor element are covered with an exterior made of an insulating resin, An insulating substrate formed over the back surface through the side surface is provided on the lower surface of the capacitor element, a wire is connected to the anode lead wire by resistance welding, and the wire and the anode terminal are connected by wire bonding. A chip-type solid electrolytic capacitor, wherein a cathode terminal and the cathode layer are connected by a conductive adhesive.